• Crop Protection
  • Apr 20, 2021

4 Ways to Upgrade Your Early-Season Spray Program

Row of nozzles on a spray boom outputting herbicide.
Once your burndown application is complete and fields are ready for planting, it’s hard to think about anything but getting seeds in the ground. For effective weed management, however, planting must be balanced with a strategic herbicide program to ensure effective weed control and minimize the development of weed resistance. Let’s take a look at a few important components that may provide room for enhancement in your program.

Set a Smart Spray Schedule 

Many farmers will apply their burndown chemistry in the same pass as their nutrients and residual control herbicide. The problem with this approach is that you not only reduce control of the targeted cover crop or weeds, you also reduce the active window of your residual chemistry by applying it so early. My recommendation is to split those applications and apply your burndown by itself, such as a 2,4-D or glyphosate, then come back in with your residual control and nutrients.
In terms of application timing for residual control, it’s best to get it done as close to planting as possible. If you’re putting it out ahead of time, which is logistically more feasible in some situations, get that application as close to the planting pass as you can to maximize the length of the residual.
For the first post-emergence application, I recommend spraying 21-28 days after your residual control application because that’s generally when weeds start coming in. It’s important to take action while weeds are small or at least before they reach 4 inches tall. Once they’re past that benchmark, they’re much more difficult to control. It may seem unnecessary to make an application before you see obstructive weed populations, but this proactive approach will pay off when your fields stay clean, and you’re not scrambling to eliminate weed competition down the line.
To keep applications on track, I recommend planning a spray schedule based on calendar dates versus visual observation. For example, if the pre-emergence application was made May 1, post-emergence applications should be scheduled for May 21 and wrapped up by May 28. When marking your calendar, remember that the goal is to get the activity of these two applications to last from planting until the canopy shades the row.

Choose the Right Nozzle for Each Application 

Selecting and calibrating sprayer nozzles is an important step to ensure even, consistent coverage across the entire spray boom and, ultimately, the entire field. While this may sound simple, there are many nozzle types and sizes available with little information about which one is best for which application, so selection can get overwhelming. To help in your decision process, here are some helpful guidelines:
  • Nozzle size is determined by three factors: rate (gallons per acre), pressure and speed of the application. Charts can be found in the back of any nozzle manufacturer’s book to help you pick the size of droplet and nozzle type you need.
  • Droplet size is determined by the type of pesticide. For contact-type chemistries, coverage is extremely important, which means higher carrier volumes and smaller droplet sizes are needed. For systemic chemistries, coverage is less critical so nozzles with lower carrier volumes and larger droplets can be used. 
Nozzles should be calibrated each spring before you head out to the field. Many farmers will visually check their nozzles to make sure they’re outputting a satisfactory spray pattern. While this method will catch many faulty nozzles, it’s hard to see when nozzles are wearing down and dispensing less than others. Calibrating doesn’t take long but will help you catch discrepancies like this and ensure each nozzle is consistently distributing product throughout the field.

Account for Factors That Impact Efficacy

For post-emergence applications, time of day is critical. Weeds will only uptake chemical if they’re actively growing, which means the most optimal growing conditions make for the most optimal spraying conditions. It’s important to note that certain herbicides are more sensitive to environmental factors than others. For example, 2,4-D and dicamba are less sensitive, while glyphosate is more sensitive and glufosinate it is extremely sensitive to time of day.
Humidity and temperature are two other major factors in efficacy. If humidity is high, the droplet stays wet on the leaf for longer, increasing opportunity for penetration. When temperatures are higher, the plants will grow more actively, allowing you to get more herbicide into both the weed and crop. In my region, centered in Eastern Iowa, I generally recommend backing down on surfactant and oil rates if you add the relative humidity and the temperature together and it equals greater than 150 because that benchmark tends to indicate an increase in crop response. However, this balance will vary based on climates and weather patterns in different regions.

Don’t Skimp on Adjuvants

Adjuvants like water conditioners and surfactants are often overlooked but can be extremely important for herbicide efficacy. Generally, chemicals that need water conditioners are referred to as a weak-acid herbicides, which means they have a negative charge that grabs onto calcium, magnesium or iron in the water and deactivates the chemical. When a water conditioner is included, it occupies that negative charge and prevents this from happening. While glyphosate is the most well-known weak-acid herbicide, people often don’t realize that 2,4-D, dicamba, glufosinate and many other chemicals also fall into this category and can be more effective if applied with water conditioners.
Surfactants are also an important tank-mix addition because they help keep the herbicide droplet wet longer and spread the droplet out on the leaf surface. Both of these actions increase penetration and absorption by the plant.
While it’s easy to be laser focused on planting in the spring, it’s important to be timely with your herbicide applications for effective control and better yields come harvest. For more guidance on early-season weed management and product selection, talk to your local WinField United retailer.

All photos are either the property of WinField United or used with permission.

© 2021 WinField United. Important: Before use always read and follow label instructions. Crop performance is dependent on several factors many of which are beyond the control of WinField United, including without limitation, soil type, pest pressures, agronomic practices and weather conditions. Growers are encouraged to consider data from multiple locations, over multiple years, and be mindful of how such agronomic conditions could impact results. WinField is a trademark of WinField United. All other trademarks are the property of their respective owners.

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